Process for the dyeing of tow in hydrated condition

ABSTRACT

A process for the continual dyeing of fibres produced by a wet spinning process, in particular for the continual dyeing of polyacrylonitril tow in a hydrated condition is disclosed in that the fibre or the fibre strand after fibre formation without previous drying is passend through a dyestuff solution or suspension which is flowing in counter current. Said process is very economical and provides without the use of any electronic controls the continual dyeing of said fibres with almost 100 percent exhaustion.

United States Patent 1191 Eigenmann et al.

PROCESS FOR THE DYEING OF TOW IN HYDRATED CONDITION lnventors: Gottfried Eigenmann, Therwil; Leo

E. Kaiser, Aesch; Otto Niithiger, Oberwil, all of Switzerland Assignee: Ciba-Geigy AG, Basel, Switzerland Filed: Oct. 31, 1972 Appl. No.: 302,504

Related US. Application Data Continuation of Ser. No. 150,754, Dec. 22, 1970, abandoned.

Foreign Application Priority Data Dec. 23, 1969 Switzerland 19173/69 us. c1. 8/177, 8/151 1111. C1... D06p 3/70 Field of Search... 8/l5l.2, 151.1, 177, 177 AB, 8/1, 151; 68/181 R References Cited UNITED STATES PATENTS Creswell 264/28 lll/ [ Jan. 22, 1974 2,949,337 8/1960 Oldershaw ..8/15l.2 3,241,343 3/1966 3,315,501 4/1967 3,353,381 11/1967 Primary ExaminerLeon D. Rosdol Assistant Examiner-T. J. Herbert, Jr. Attorney, Agent, or Firm-E. F. Wenderoth et al.

[57] ABSTRACT A process for the continual dyeing of fibres produced by a wet spinning process, in particular for the continual dyeing of polyacrylonitril tow in a hydrated condition is disclosed in that the fibre or the fibre strand after fibre formation without previous drying is passend through a dyestuff solution or suspension which is flowing in counter current. Said process is very economical and provides without the use of any electronic controls the continual dyeing of said fibres with almost 100 percent exhaustion.

1 Claim, 2 Drawing Figures PROCESS FOR THE DYEING OF TOW IN HYDRATEI) CONDITION This is a continuation of application Ser. No. 100,754, filed Dec. 22, 1970, now abandoned.

Polyacrylonitrile fibres are produced by the so-called dry spinning process in which the fibre is produced from polymers dissolved in organic solvents by evaporating the solvent, or they are obtained by the so-called wet spinning process in which the fibre is precipitated in aqueous solution with the addition of electrolytes. In the so-called wet spinning processes, directly following the actual fibre-forming process (spinning process), the fibre is first subjected to several washings and then to a stretching process in order to orientate the macromolecules before it is dried. In this swollen condition, the fibre is to a very high degree capable of ab sorbing the dyestuff, e.g. in an aqueous bath. In this state the dyeing can thus be performed under substantially milder conditions than are necessary for dyeing the same fibre after the spinning process when the fibre has been dried. Thus dyeing of tow in a hydrated condition saves energy and time; in addition a drying process can be eliminated.

Processes for the dyeing of fibres in a gel-like condition which hitherto have been known consist essentially of bringing the fibres in contact with the dyestuff solution either on a padding mangle or in a simple dyebath and then washing hot. Since in a continuous process, dyestuff is continually being removed from the dyebath, in the known processes specific measures must be taken to guarantee a constant concentration of dyestuff in the dyebath in order to obtain a specific shade. Such operations as, eg measuring the concentration of the dyestuff and regulating the additional amounts of concentrated dyestuff required, e.g. by means of an electronic regulating arrangement are unavoidable. When a dyestuff mixture is employed, as is usually the case, it is necessary to dose the additional amounts of the several dyestuffs individually according to their dyeing behaviour andthus the individual dyestuff solutions must be controlled separately. Such regulating arrangements are very complicated and expensive, and often the dosed amounts tend to vary.

It has now surprisingly been found that fibres produced by wet spinning processes, in particular polyacrylonitrile tow, can be continually dyed in a hydrated condition in a simple manner by passing the fibre, or fibre strand, after its formation and without drying it, through a dyestuff solution which is flowing in counter current. This counter current principle is, for example, known in so-called cascade washers in the production of fibres.

The application of the counter current principle to the dyeing of tow in a hydrated condition is very economical. Furthermore, without the use of any electronic controls, it permits the continuous dyeing in a simple manner of the said fibres in specific shades and with almost 100 percent exhaustion.

The process can, for example, be performed in an apparatus which is characterized by a series of communieating containers; a means for conveying the fibre strands through these containers; a means for feeding the dyestuff solution, which means opens into the last container relative to the direction of conveyance; the containers being equipped with baffle plates which direct the flow of the dyestuff solution in the direction opposite to the path of conveyance.

Such an arrangement is illustrated, for example, more in detail in the drawing:

FIG. 1 shows (in a diagramatic representation in sec tion) an example of an embodiment of the apparatus according to the invention for the performance of the counter current dyeing, and

FIG. 2 shows a section along the line I! II of FIG. 1.

The dyeing aggregate shown consists essentially of a series of containers S S S,,, a conveying device 6H for fibre strands F leading through these containers, a mixer L for the preparation of the dyestuff solution. and a proportioning pump K. The outlet of the mixer is connected via the proportioning pump with the last container S, relative to the direction of conveyance. The containers S,,, S,, ...S communicate with each other via overflow channels D. Baffle plates C which force the dyestuff solution to flow in the direction opposite to the path of conveyance are mounted in the containers. The first container is provided with an outlet E which is preferably a type of overflow. M designates a double jacketed heating means controlled by a thermostat for the series of containers.

This dyeing aggregate functions as follows.

The supply of mixed dyestuff solution in mixing tank L is passed after optional dilution via the proportioning pump K to point A of the last container of the dyeing aggregate. The solution is forced by the baffle C in counter current direction to flow downward past point B and then at point D of the last container into the next to last container. The liquor then passes through all of the containers in the same manner and finally leaves the first container at point E. The fibre material, which has received the usual treatment after the spinning process, comes from point F over the guiding rollers G and H and is dipped into the first container. The time spent in this container is determined on the one hand by the speed of the conveyance of the fibre and on the other hand by the dimensions of the individual containers. It should be in the order of from about 0.1 to 30 seconds. The fibre is thus brought into contact with the last concentrated dyestuff solution, absorbs a certain amount of dyestuff, then moves on to the next container where the dyestuff concentration is higher. In this manner at the end of the nth container, the fibre comes in contact with fresh dyestuff solution so that after an equilibrium has been attained, the depth of shade of the material leaving at point I is constant. The guiding roller G and H should be constructed in such a manner that the tow is spread out as widely as possible when passing through the individual containers in order to obtain an optimal penetration of the dyestuff solution in the tow.

The depth of shade is controlled on the one hand by varying the concentration of the dyestuff solution in mixing tank L and on the other hand by varying the amount of solution dosed by proportioning pump K. With a constant concentration in tank L and a constant dosing, there is an equilibrium of the concentration in the individual containers, which decrease from container (n) to container (n-l l). The optimal adjustment is reached when the concentration of the dyestuff solution leaving at point E is zero or at least almost zero, since in this manner an almost complete utilization of the dyestuff is attained. The time required until equilibrium is reached depends on the size of the individual containers, the smaller the volume of the containers, the less time is needed. Since the velocity of the dyeing process as well as the equilibrium of the concentrations attained on the fibre depend on the temperature of the dyebath, it is advantageous to surround the entire dyeing aggregate with a jacket M which is controlled by a thermostat. For the performance of the dyeing of hydrated polyacrylonitrile tow, it should permit a constant temperature to be kept in the range between and 70C.

The advantage of the new dyeing process described are that the dyestuff employed can be practically completely utilized and that there is no fluctuation of the depth of shade of the material leaving at I, such as is the case with systems depending on the measurement of a value and a regulation derived from that measurement (additional dosing). In addition the problems of uneven end results are avoided, sinde each section of the fibre material comes in contact with fresh dyestuff solution at the end of the dyeing process.

The dyebaths usual in practice may be used in the process according to the invention. It is convenient to prepare them by dissolving or dispersing the dyestuff in water and adjusting the pH of the dyebath obtained with an acid and/or a buffer salt to the desired value.

Disperse dyestuffs as well as anionic and in particular cationic dyestuffs may be used according to the invention. Dyestuffs of any class may be used.

Disperse dyestuffs which may be used according to the invention are preferably azo dyestuffs, as well as anthraquinone, nitro, methine, styryl or azostyryl dyestuffs.

Suitable as anionic dyestuffs in the process according to the invention are any class of the so-called acid wool dyestuffs as well as of substantive dyestuffs in which the coloring constituent is in the anion such as the alkali or ammonium salts of dyestuff sulphonic or carboxylic acids, i.e. metal-free or metallized sulphonated monoazo or disazo dyestuffs, in which are also included the formazane dyestuffs, their chromium, cobalt, nickel and copper complexes, as well as sulphonated anthraquinone, nitro and phthalocyanine dyestuffs.

Cationic dyestuffs which may be used according to the invention are advantageously the technically easily obtainable salts and metal halides, for example the zinc chloride double salts, of known basic dyestuffs. These are, for example, dyestuffs containingv onium groups such as thiazines, oxazines, diphenyl methanes, triphenyl methanes, rhodamines, azo and anthraquinone dyestuffs, preferably monoazo, methine, azomethine and anthraquinone dyestuffs, the onium groups being preferably ammonium groups.

The following examples illustrate the invention. Temperatures are given therein in degrees centigrade. Examples Dyeing is performed in a dyeing aggregate consisting of five elements S to S connected in series, constructed in such a way that the tow has a dip time of 0.7 second per element when it is passing at a rate of 0.5 meter per second. This corresponds to a dip length of 0.35 m/element. Such an aggregate is illustrated in H0. 1, the individual elements S to 8,, however, are arranged in cascade form.

The dyeing aggregate is continually charged at G with polyacrylonitrile tow which has been produced from a solution of polyacrylonitrile in sodium thiocyanate by the wet spinning process, and has been stretched, as is usual in industry, at then washed but not dried. The water content of the tow is reduced by squeezing out the excess to about percent of the dry weight. The amount of tow entering the dyeing aggregate at G can be seen in Table II.

An aqueous solution is a dyestuff, the composition of which is given in Table ll, is mixed in feed tank L, and then mixed in a constant proportion with the proportioning pump K in a T-shaped mixing element together with a constant proportion of water, and introduced at A to element S care being taken that the dyestuff solution is spread over the complete width of the apparatus.

The tow which enters the elements S to S at G in a colorless state is successively dyed in the individual elements and is completely dyed as it leaves the aggregate at l.

The dyestuff solution which has remained on the tow is removed by two squeezing rollers and discarded. The dyed tow is then rinsed for a short time in hot water and then dried. The concentration of the dyestuff solution slowly decreases from element S to S so that the dyestuff solution leaving the aggregate at E is colorless or almost colorless.

If, when the aggregate is put into operation, the elements are first all filled with water, an equilibrium of the dyestuff concentration is reached in the individual elements after several minutes. After equilibrium has been reached, when the dosing rate and the dosing concentration remain constant, the shade of the dyed tow remains constant even over a long period of time.

The following Table I gives the structures of the dyestuffs used:

TABLE I I Dyestulf of the formula II Dyestufi of the formula III Dyestufi of the formula.

IV Dyestufi of the formula V Dyestufi of the formula H O O 4 meagre-NC VI Dyestufl of the formula.

0 NHCH;

Y NHGHaCHzOH VII Dyestutf of the formula.

VIII Dyeslsufl of the formula.

The following Tahle ll gives the components used in Dosage, water Examples 1 to 9, the amounts thereof and the dyeing conditions used. At the end of each Example, the shade of the polyacrylonitrile fibre dyed according to the invention is given.

Examples Dyestuft I l l Concentration of stock solution 43 g/l 43 gll 43 gll Acetic acid. cone. 2 3]! 2 gll 2 g/l Sodium acetate, conc. 2 g/l 2 g/l 2 g/l Temperature 30C 30C 30C Dosage, stock solution H0 ml/min ll0 ml/min l ml/min Dosage, water l700 ml/min i700 ml/min 850 ml/min Water temperature 25C 50C 50C Temperature in Elements S -S 36-25C 4842C 48-42C Amount of polyacrylo- 430 g/min 430 g/min 430 g/min rutnle tow mam Relative dyestulT concentration in equilibrium Element S 69 77 Element S 54 44 42 Element S; 28 25 l8 Element S, 10 l2 7 Element S 4 7 3 Squeezed solution removed 1.6 0.2 0.5 Exhaustion 93 96 Depth of shade attained L05 1.02 L06 Shade of the dyed polydark dark dark acrylonitrile fibre red red red Key: conc. at introduction 100 Dyestuff calculated on the weight of the dry fibre Examples 4 5 6 Dyestuff ll ll [.5 g/l lll 4.3 g/l I 3.8 g/l IV 0.l2 g/l lll 6.l g/l Concentration of stock solution g/l Acetic acid, cone. 3 g/l 2 gl] 6 g/l Sodium acetate, cone. 3 gl] 2 gl] 2 g/l pH 4.6 3.4 3.7 Temperature 35C 30C 22C Dosage, stock solution 260 ml/min 100 ml/min l30 L ml/min SOaN8 850 ml/min 800 ml/min 800 ml/min Water temperature 30C ca.25 C ca. 25C Temperature in Elements S -S,, 38-32C 38-26C 3725C Amount of polyacrylo- 430 glmin 430 g/min 430 g/min HA I nitrile tow Relative dyestuff concentration in equilibrium 'Exh'auiio'n 77?) 9s"6 '98 5;, Depth of shade attained 4.4 0.24 0.13 Shade of the dyed polyyellow grey blue acrylonitrile fibre Key: in V cone. at introduction Dyestuff calculated on the weight of the dry fibre X Optical brightener of the formula o-soicin e N O (CHJ):NCHICHgCH:-N H

XI Optical brightener of the formula N N s out A H O CHr-CH:NL l NH CH=C H HN- I N CHgCHg-O H N N H CH: s

" Examples 7 8 9 TABLE iii M v 1 an. Exam les 35 g/l vii 25 p H 88 1 Optical brightener X XI VI I Concentration of stock solution 4 gl] 5 g/l Dyesm 7 IX Acetic acid, conc. 0.5 g/l g, 62 8/ Sodium acetate, cone. 0.5 g/l pH 4.6 6.2 ::ci:n;;ziitlioi0:fcstock solution I I I 30 Temperature I us Dosage, stock solution ll0 ml/min I40 mI/min 6 8 6 4 6 4 Dosage, water I700 ml/min I400 ml/min g "alum d o' ssc c Water temperature 25C 50C Dosape stock solufion '65 Temperature in Elements S,S 3625C 4842C g mumin H0 Amount of polyacrylonitrile tow 430 g/min 430 g/min mI/min 60 Relative concentrations of mllmin 35 optical brightener in equilibrium Dosage wamr 700 Element S, 56 58 mum", I250 Element s. 36 42 ml/min 1700 Element S, mllmin Element S, 6 7.2 Water temperature 55C C 55C Elcmem SI 2 Temperature in Elements s. -s, 42-53c 3s 28C 43-S4C q e wlumm removed Amount of polyacrylo- 430 Exhaustion 98 96 glmin 430 Optical brightening effect 0.l 0 l5 g/min430 1mi Treated polyacrylonitrile fibre white white nitrile tow brightened brightened Relative dyestuff concentration" Key: in equilibrium cone. at introduction [00% Elemem 2 Optical brightener calculated on the weight of the dry fibre Element S. 45 Element S, A V w 7W V rrrr .v Ei 'ffiflifi? 1 What we claim 1S2 Element S, ll w H A. q q solution removed 6 4 a- 8 l. A process for the continuous dyeing of a polyacryl- 88 ca onitrile fiber or fiber strand in a hydrated condition,

84 produced by a wet spinning process after riber forma- De th of shade attained l 4 I96 0 s7 shfdc 0mm dyed pom g'reen red ofmnge .tion but without being previously dried, which comaerylonitrile fibre Key: eonc. at introduction l00% Dyestuff calculated on the weight of the dry fibre The present process is also suitable for the optical brightening of fibres which have been produced by a wet spinning process. Dispersable anionic and, in particular, cationic optical brighteners are suitable for use in the process according to the invention. Various classes of these brighteners may be used. Especially brilliant optical brightening effexts are obtained with anionic compounds derived from the stilbene class and with cationic compounds derived from the courmarin class.

prises passing said fiber or fiber strand through a dyestuff solution or suspension following in countercurrent, wherein a dye solution or suspension of constant. concentration is introduced at constant rate at the place where the fiber leaves the dyestuff solution or suspension and the relative velocity of the fiber to the dyestuff solution or suspension is so adjusted that at that point where the fiber enters the dyestuff solution or suspension, the dyebath has a concentration of zero, or substantially zero, and the dyeing is performed at a constant temperature in the range between 20 and C. 

